I’ll be staying near my home in Manhattan this week. But if I did have plans to travel by airplane for the holiday, I think I’d be apprehensive about the new screening procedures implemented by the Transportation Safety Authority (TSA).

My concern is not so much with the scanners. (For a detailed review of these machines, I recommend this article in Popular Mechanics.) There are two types of scanners in current use: millimeter wave machines, which use radio-frequency waves to generate 3-D images, and back-scatter units which, by design, use low doses of x-rays to visualize what’s inside a person being scanned.

Rather, I’m worried about screening errors – false positive and false negative results, and about harms – physical and/or emotional, that patients and people with disability may experience during the screening process.

In the context of travelers’ screening, a false positive occurs when an examiner thinks he or she sees or feels something abnormal – say a weird expression on a passenger’s face or when an initial, low-threshold alarm goes off somewhere in the system – but the person isn’t carrying any dangerous or contraband items. That early, false positive signal puts the traveler through extra procedures, possible embarrassment and/or stress.

A false negative happens when a screener misses an explosive device or other harmful material. A good example is the so-called Christmas bomber, who last year got through airport security and boarded a plane with explosives effectively hidden in his underwear. In that December 2009 instance, the examiners failed to identify a passenger who carried a potentially lethal weapon. The TSA’s goal should be to minimize the number of false negative screening tests. That’s because we wouldn’t want someone to get through screening and board a plane while carrying a weapon.

The problem is that it’s easy to imagine an imperfectly-trained, inexperienced or just plain tired screener missing an irregularity in someone’s 3-D or other kind of whole-body image, especially in the context of a steady stream of passengers rushing to catch flights. The operators might miss weapons despite the visual “information” available, right in front of their eyes.

So I don’t object to the new technology, which should increase the accuracy of the screeners’ function. Ultimately, though, we can’t get around the fact that TSA employees are human and some will be nearing the end of their shift; the scanners can reduce but not eliminate these kinds of errors.

My second concern is with the potential harm to patients and people with disabilities. People may be harmed physically if, for example, a screener mishandles a pump or other device. There’s been a lot of attention to one recent report, that of a 61 year old man with a history of bladder cancer whose urostomy bag ruptured during an airport pat-down. The man described his urine spilling, and his feeling humiliated.

This is a very understandable reaction; as someone who has implants after mastectomies, and who carries a lot of internal metal hardware in her spine and elsewhere, with scars galore, I know how damaging can be a stranger’s scrutiny. Unlike doctors and nurses, most TSA employees are not accustomed to seeing colostomy bags, stumps and other disfigurements usually hidden under a person’s clothing. Even an accidental, unkind expression in a look-over, or an insensitive pat-down, could make a person feel pretty bad about their ailment.

Of course we don’t have to travel on airplanes. I don’t see this as a civil rights issue; I don’t think there’s a right to board a public vehicle without full screening if the TSA deems it’s necessary for public safety. Rather, I accept that an aspect of having illnesses is that sometimes you have to put up with things other people don’t experience.

What would help, clearly, is better sensitivity and training of TSA staff, as was considered in response to the urostomy incident. But given the huge volume of travelers and enormousness of our complicated transportation system, it seems unlikely we’ll get a satisfactory solution among all staff at all airports, at least not in time for Thanksgiving.

From the patient’s perspective, there are some practical points that might help. Amy Tenderich, at Diabetes Mine, offers tips for individuals with insulin pumps. Trisha Torrey has an interesting piece on her Patient Empowerment blog (where she argues that this is not an empowerment issue) and recommends a simple, common-sense approach, which is to arrive early at the airport. As for me, I carry cards indicating the dates of my surgeries and the nature of my hardware. Now, I’ll add to those a note from my doctor.

Meanwhile I hope the screeners will use their new equipment to do a better job at detecting people carrying weapons. And that those individuals who plan to boycott the scanners with a National Opt-Out Day tomorrow, will change their minds. The TSA employees have enough on their hands already, without a demonstration; it’s in everyone’s interest that the screening be effective, hopefully 100 percent, in this holiday season.